EFFECTS OF COMBINED COLD AND HYPERBARIC-OXYGEN STORAGE ON FREE-FLAP SURVIVAL

We have previously reported that hyberbaric oxygen (HBO) improved the survival rate of experimental free flaps. The purpose of this study wa s to evaluate the effects of combined hypothermia and HBO administered during storage on free flaps and on the xanthine oxidase system in ra ts. Epigastric skin flaps were stored cold for 48 and 72 hours either in room air or under HBO (2.9 atmospheres absolute, 100% oxygen) befor e free flap transfer. The success rates of free flaps were 80% (8/10) after 48 hours and 20% (2/10) after 72 hours of cold storage in room a ir. HBO produced no effect after 48 hours but significantly increased the success rate to 70% (7/10) after 72 hours of cold storage. Tissue hypoxanthine (plus xanthine) levels increased to 210% of normal after 48 hours of cold storage in room air and to 176% in HBO. Elevated hypo xanthine levels returned toward normal by 72 hours of cold storage in room air, while the increased levels remained under HBO. Xanthine oxid ase activities significantly increased by 60 to 80% during 72 hours of room air storage. HBO treatment inhibited xanthine oxidase activity t o 48% of normal by 72 hours of storage. Free flaps exhibited no signif icant alterations in Gr and G6PDH activity after 48 hours of cold stor age in room air or HBO. After 72 hours of cold storage, the room air c ontrol displayed a trend of decreasing GR activity and a significant 2 0% decrease in G6PDH activity, wile HBO groups showed no significant a lterations in both GR and G6PDH activity compared to normal. Protectio n of the antioxidative enzymes by hypothermia and inhibition of the xa nthine oxidase activity by HBO appear to be one of the mechanisms of i mproved skin flap survival in free flaps. (C) 1994 Wiley-Liss, Inc.